Some wireless communication systems, such as Long Term Evolution (LTE) system, utilize a concept referred to as Automatic Neighbour Relations (ANR). Similar concepts also exist for other cellular radio communication systems, such as Global System for Mobile communications (GSM), Code Division Multiple Access (CDMA) or the like. In LTE, ANR enables automatic discovery of neighbour relations between cells and between so called evolved-NodeBs (eNBs), commonly referred to as base stations. A purpose of ANR is to identify and establish interfaces to those of the discovered neighbours that are deemed appropriate according to various measures. Thanks to the interfaces, such as inter-eNB interfaces referred to as X2 interfaces in LTE, neighbour parameters can be configured. The neighbour parameters, such as threshold values and/or measurement values of signal strength, path-loss, Signal-To-Interference-and-Noise-ratio etc., may be used for e.g. handover, Coordinated Multi-Point (CoMP) transmission, Inter-Cell Interference Coordination (ICIC), load balancing or the like.
The concept of ANR includes that an eNB requests a user equipment (UE) to measure on and read Physical Cell Identities (PCIs) of nearby cells as well as to measure on and read at least parts of system information broadcast by those nearby cells. The PCIs and/or the parts of the system information are reported back to the eNB by the UE. Thanks to the PCIs and/or the parts of the system information, the eNB can determine whether or not any of the nearby cells are indeed suitable as neighbours and the eNBs can also automatically establish a relationship and an X2 interface between involved eNBs when needed. ANR in LTE is further described in chapter 22.3.3 in Third Generation Partnership Project (3GPP) Technical Specification (TS) 36.300.
Above, the concept of ANR has been described in relation to a 4th generation (4G) telecommunication system, such as LTE. However, a similar feature as ANR would be equally useful and beneficial in a 5th generation (5G) system.
A difference between the 4G and 5G systems relates to frequency bands that can be used. The frequency band used has implications for design of the 5G systems. Due to expected lack of available radio spectrum, frequency bands located at very high frequencies, such as 10 GHz and above, are planned to be utilized for future mobile communication systems, including the 5G systems. Attenuation of radio signals at these very high frequencies can be much greater than attenuation of radio signals at lower frequencies. Amount of the attenuation may be affected by e.g. atmospheric penetration properties, diffraction properties and the like.
As a consequence of the very high frequencies, energy of radio signals in these future mobile communication systems will increase, since energy is proportional to frequency according to the well-known Planck-Einstein relation. Increased energy of radio signals will in turn cause a measure of receiver antenna aperture to decrease, since the receiver antenna aperture is inversely proportional to energy per area unit of the radio signals. The receiver antenna aperture describes effective receiver antenna area collecting electromagnetic energy from an incoming electromagnetic wave, such as the radio signals. This means that due to decreased receiver antenna aperture, a link budget for a transmission becomes worse—even in a free space scenario disregarding the aforementioned attenuation at the very high frequencies—while it is assumed that omnidirectional receive and transmit antennas are used. The link budget accounts for gains and losses of a radio signal transmitted, by a transmitter, through e.g. the atmosphere or even free space, and received at a receiver, while considering e.g. the receiver antenna aperture.
Instead of using omnidirectional antennas, the 5G system are capable of using antennas adapted to provide beamforming, whereby loss of link budget at the very high frequencies may be compensated for. Beamforming may be used at the transmitter, at the receiver, or both. In a large part of the radio spectrum for 5G systems, the preferred configuration is to use a large antenna array at an Access Node (AN) and a small number of antennas at the UE. The large antenna array at the AN enables high-order transmit beamforming in the downlink and the small number of antennas at the UE enables some low-order transmit beamforming.
For these reasons, e.g. 5G systems are expected to make heavy use of high-gain and narrow beamforming to provide transmission at high data rates and enhanced coverage. For example, thanks to the beamforming a distant user may be served at a high data rate, while the distant user would otherwise not be realistically covered with normal sector-wide beams, i.e. without high-gain and narrow beamforming.
Another difference between 5G and 4G systems is that for 5G systems a lean design principle is emphasized more and much better energy efficiency is required. The lean design principle favours attempts to avoid always-on transmissions for the purpose of energy efficiency.
In view of the above, a problem may be related to how to adapt ANR of LTE to the 5G systems.